Deeper tones come from larger pipes. If you are staying with duals, I'd go no larger than 2.25" pipe for a stock-mild engine, or just a single 3" pipe. I had a single 3" to a dual 2.5" out Flowmaster 50 series on my Dakota R/T and with a gutted 3" cat it was LOUD and deep too. I'm not a big fan of the Fartmaster sound anymore though. I suggest trying the Dynomax Ultraflow or Hooker Aerochamber mufflers.